TUCSON, Ariz.—Rep. Martha McSally said she was sexually abused by a coach when she was in high school, an experience that she said shaped some of the biggest decisions in her life.

Ms. McSally, a Republican who is running for the Arizona U.S. Senate seat being vacated by GOP Sen. Jeff Flake, has spoken before of being sexually harassed during her 26 years in the Air Force, where she became the first female pilot to fly in combat. But she hasn’t previously discussed publicly her high-school track coach’s alleged sexual abuse of her when she was 17, which she said she didn’t tell her friends or family about until a decade later.

“It took a while for me to come to a place where I understood what the hell I had been through,” Ms. McSally, now 52 years old, said in an interview with The Wall Street Journal. “At the time, I was so afraid. I now understand—like many girls and boys who are abused by people in authority over them—there’s a lot of fear and manipulation and shame.”

The national debate over sexual harassment swept Capitol Hill in the past year, but more attention has centered on allegations of lawmakers’ misconduct than their own experiences as alleged victims of sexual abuse.

The congresswoman brought up the alleged sexual abuse in an interview this month at a Mexican restaurant in Tucson regarding her history as a longtime runner and said it was an inextricable part of her relationship with the sport. “Running is a place where I was violated, but running is also a place where I found healing and found strength and resolve,” she said.

Ms. McSally said the experience occurred during her senior year of high school. She attended St. Mary Academy-Bay View, an all-girls Catholic school in Riverside, R.I. Her father had died when she was between sixth and seventh grades and, to “escape from the grief of losing my dad,” she turned to exercise, including swimming and running, she said.

In high school, she ran cross-country and track, and discovered her talent for throwing the javelin. One of her first running coaches had become a father figure for her, she said, and when a different coach succeeded him, she put the same kind of trust in him.

Two decades older than her, the new coach pressured Ms. McSally into having sex with him, she said in the interview. As she grew increasingly uncomfortable with the situation, he used a variety of psychological tactics to keep her silent, according to Ms. McSally.

“Even though he didn’t physically force me, it certainly was an emotional manipulation,” Ms. McSally said. She intensified her running in an effort to shut down her menstrual cycle, which she had noticed disappeared when she ran longer distances. “I was freaking out that he would get me pregnant,” she said.

The school’s 1984 yearbook identifies the track coach as Jack Dwyer, a spokeswoman for St. Mary Academy-Bay View said, but she declined to comment further. Mr. Dwyer said he coached Ms. McSally, and he denied her allegations.

“I believe she’s nuts,” he said. “That girl is the most scheming woman I ever met.” Mr. Dwyer said Ms. McSally came to his home “a few times, uninvited, with and without other people,” but they never had sex, he said. “This is another of her little schemes to make her look like this has happened to her,” he said.

In response, Ms. McSally said in a statement: “He is a troubled man who I have forgiven, and I hope he finds God’s peace and grace.”

St. Mary Academy-Bay View President Marybeth Beretta and Communications Director Sara Del Signore didn’t respond to requests for comment about Ms. McSally’s allegations and the former coach.

At the time, Ms. McSally, said in the interview, she told only two adult women about what was happening, but none of her close friends or family. One of those women said she was alarmed by what she heard, and she told the school’s principal about the coach’s alleged behavior, without naming Ms. McSally.

The school immediately fired Mr. Dwyer, the woman said in an interview. Mr. Dwyer denied the woman’s comments and said he resigned to take another job.

Ms. McSally became the first female fighter pilot to fly in combat in 1995 and the first woman to command a combat aviation unit in 2004.
Photo:
Maura Friedman for The Wall Street Journal

The experience helped Ms. McSally make a career-defining choice, she said: She entered the Air Force Academy in Colorado, where she had been recruited to throw the javelin.

“One of the many reasons why I ended up leaving Rhode Island and going to the Air Force Academy was to get away from him,” Ms. McSally said. “I needed to geographically get to another place.”

Roughly 10 years later, in the mid-1990s, Ms. McSally said, she explored whether legal avenues were available to hold the coach accountable and found out there were few.

Because she had been 17 at the time, the coach couldn’t be accused of statutory rape under Rhode Island law, which criminalizes most consensual sex with individuals under 16. Alleging sexual assault and abuse of power also looked challenging. “That’s difficult to prove the morning after, let alone 10 years after,” Ms. McSally said, adding that the statute of limitations, which has exceptions for some sexual assault, would also be a hurdle. Her only legal option appeared to be filing a civil lawsuit for damages, which didn’t appeal to her.

She had told her friends and family and felt like she “was in a healthy place. I’m not going to go into a court,” she said. She let the idea of legal action drop.

Rich Robinson, who worked for a nonprofit that volunteered at the chapel at Davis-Monthan Air Force Base in Arizona when Ms. McSally was stationed as a pilot there, said Ms. McSally told him about the alleged abuse by the coach around 1994.

Ms. McSally completed a full Ironman triathlon in 1993.

During a run, “Martha shared some things about her past,” said Mr. Robinson. “She shared that she had been violated by a high-school coach and others,” he said, referring to her later experiences in the Air Force. Ms. McSally told the Journal in the interview this month that she encountered “similar, awful experiences in the military on the spectrum of abuse of power and sexual assault.”

Later, when Ms. McSally was running for Congress and set up a
Facebook
page, she said, she realized the coach had sent her a friend request—and that there were pictures of her on his own Facebook page. She left him a message asking him to remove all images of her, and he complied, she said. Ms. McSally said it was their only contact in three decades.

“I left a pretty scathing message, but I also told him that I forgave him in that same message,” she said. “Not because he deserved it…forgiveness is about freeing yourself—not allowing any sort of deep anger to have power over you.”

More recently, Mr. Dwyer coached track in the Exeter-West Greenwich Regional School District, until he resigned last spring, according to the district’s superintendent, James Erinakes. His record there included no allegations of sexual abuse, Mr. Erinakes said.

Looking back, Ms. McSally said, the ordeal pushed her to challenge herself in other ways. She completed a full Ironman triathlon in 1993, became the first female fighter pilot to fly in combat in 1995 and the first woman to command a combat aviation unit in 2004.

Ms. McSally said she believes she became “an endurance athlete and a fighter pilot because I was looking for ways to not be powerless.”